Showing papers by "Zhihua Chen published in 2017"

Features of spillover networks in international financial markets: Evidence from the G20 countries

Abstract: The objective of this study is to investigate volatility spillover transmission systematically in stock markets across the G20 countries. To achieve this objective, we combined GARCH-BEKK model with complex network theory using the linkages of spillovers. GARCH-BEKK model was used to capture volatility spillover between stock markets. Then, an information spillover network was built. The data encompass the main stock indexes from 19 individual countries in the G20. To consider the dynamic spillover, the full data set was divided into several sub-periods. The main contribution of this paper is considering the volatility spillover relationships as the edges of a complex network, which can capture the propagation path of volatility spillovers. The results indicate that the volatility spillovers among the stock markets of the G20 countries constitute a holistic associated network, another finding is that Korea acts a role of largest sender in long-term, while Brazil is the largest long-term recipient in the G20 spillover network.

Effectiveness and safety of PD-1/PD-L1 inhibitors in the treatment of solid tumors: a systematic review and meta-analysis.

Abstract: // Xiaohui Wang 1,2,* , Zhengqiang Bao 1,2,* , Xiaoju Zhang 3,* , Fei Li 1 , Tianwen Lai 1 , Chao Cao 1 , Zhihua Chen 1 , Wen Li 1 , Huahao Shen 1,4 and Songmin Ying 1,2 1 Department of Respiratory and Critical Care Medicine, Second Affiliated Hospital, Institute of Respiratory Diseases, Zhejiang University School of Medicine, Hangzhou, China 2 Department of Pharmacology, Zhejiang University School of Medicine, Hangzhou, China 3 Department of Respiratory Medicine, Zhengzhou University People’s Hospital, Henan Provincial People’s Hospital, Zhengzhou, China 4 State Key Laboratory of Respiratory Diseases, Guangzhou, China * These authors have contributed equally to this manuscript Correspondence to: Songmin Ying, email: // Huahao Shen, email: // Keywords : PD-1, PD-L1, nivolumab, pembrolizumab, cancer Received : August 12, 2016 Accepted : March 01, 2017 Published : May 31, 2017 Abstract Background: PD-1/PD-L1 inhibitors have been implicated as potentially effective anti-cancer therapies Some clinical randomized controlled trials (RCTs) have been completed for a variety of PD-1/PD-L1 inhibitors to treat various malignancies, and more RCTs are still under way We carried out this systematic meta-analysis to evaluate the efficacy and safety of PD-1/PD-L1 inhibitors in the treatment of solid tumors Methods: We searched PubMed, EMBASE, clinical trial registers, conference reports, and related reviews Eligible RCTs that compared PD-1/PD-L1 inhibitors with other chemotherapy agents or placebo in solid tumor patients were included For each RCT, progression-free survival (PFS), overall survival (OS), objective response rate (ORR), disease control rate (DCR), stable disease rate (SDR), progressive disease rate (PDR), and adverse events (AEs) were pooled for meta-analysis Findings: Based on an analysis of 10 eligible RCTs, PD-1/PD-L1 inhibitors were found to significantly improve PFS (Hazard ratio (HR), 065; 95% confidence interval (CI) 053 to 079, P <0001), OS (HR, 069; 95%CI 062 to 076, P <0001), and ORR (Risk Ratio (RR) 2 92; 95% confidence interval (CI) 206 to 415, P <000001) in all populations, including melanoma and NSCLC subgroups However, they failed to increase the DCR of cancer patients (RR 115; 95%CI 091 to 145, P =025) Furthermore, less AEs were observed in the PD-1/PD-L1 inhibitor groups than the control groups Interpretation: PD-1 inhibitors are more effective for improving the PFS, OS, and ORR of cancer patients with little toxicity, despite having little effect on increasing of the DCR

Cultivation of algal biofilm using different lignocellulosic materials as carriers.

Abstract: Algal biofilm technology is recently supposed to be a promising method to produce algal biomass as the feedstock for the production of biofuels. However, the carrier materials currently used to form algal biofilm are either difficult to be obtained at a low price or undurable. Commercialization of the biofilm technology for algal biomass production extremely requires new and inexpensive materials as biofilm carriers with high biomass production performances. Four types of lignocellulosic materials were investigated to evaluate their performance of acting as carriers for algal cells attachment and the relevant effects on the algal biomass production in this study. The cultivation of algal biofilm was processed in a self-designed flat plate photo-bioreactor. The biofilm production and chemical composition of the harvested biomass were determined. The surface physics properties of the materials were examined through a confocal laser-scanning microscopy. Algal biomass production varied significantly with the variation of the carriers (P < 0.05). All the lignocellulosic materials showed better performances in biofilm production than poly methyl methacrylate, and the application of pine sawdust as the carrier could gain the maximum biofilm productivity of 10.92 g m−2 day−1 after 16-day cultivation. In addition, 20.10–23.20% total lipid, 30.35–36.73% crude proteins, and 20.29–25.93% carbohydrate were achieved from the harvested biomasses. Biomass productivity increased linearly as the increase of surface roughness, and Wenzel’s roughness factor of the tested materials, and surface roughness might significantly affect the biomass production through the size of surface morphology and the area of surface (P < 0.05). The results showed that lignocellulosic materials can be efficient carriers for low-cost cultivation of algal biofilm and the enhancement of biomass productivity.

Bcl-2 Inhibitors Reduce Steroid-insensitive Airway Inflammation.

Abstract: Background Asthmatic inflammation is dominated by accumulation of either eosinophils, neutrophils, or both in the airways. Disposal of these inflammatory cells is the key to disease control. Eosinophilic airway inflammation is responsive to corticosteroid treatment, whereas neutrophilic inflammation is resistant and increases the burden of global health care. Corticosteroid-resistant neutrophilic asthma remains mechanistically poorly understood and requires novel effective therapeutic strategies. Objective We sought to explore the underlying mechanisms of airway inflammation persistence, as well as corticosteroid resistance, and to investigate a new strategy of effective treatment against corticosteroid-insensitive neutrophilic asthma. Methods Mouse models of either eosinophil-dominated or neutrophil-dominated airway inflammation were used in this study to test corticosteroid sensitivity in vivo and in vitro . We also used vav–Bcl-2 transgenic mice to confirm the importance of granulocytes apoptosis in the clearance of airway inflammation. Finally, the Bcl-2 inhibitors ABT-737 or ABT-199 were tested for their therapeutic effects against eosinophilic or neutrophilic airway inflammation and airway hyperresponsiveness. Results Overexpression of Bcl-2 protein was found to be responsible for persistence of granulocytes in bronchoalveolar lavage fluid after allergic challenge. This was important because allergen-induced airway inflammation aggravated and persisted in vav–Bcl-2 transgenic mice, in which nucleated hematopoietic cells were overexpressed with Bcl-2 and resistant to apoptosis. The Bcl-2 inhibitors ABT-737 or ABT-199 play efficient roles in alleviation of either eosinophilic or corticosteroid-resistant neutrophilic airway inflammation by inducing apoptosis of immune cells, such as eosinophils, neutrophils, T H 2 cells, T H 17 cells, and dendritic cells. Moreover, these inhibitors were found to be more efficient than steroids to induce granulocyte apoptosis ex vivo from patients with severe asthma. Conclusion Apoptosis of inflammatory cells is essential for clearance of allergen-induced airway inflammation. The Bcl-2 inhibitors ABT-737 or ABT-199 might be promising drugs for the treatment of airway inflammation, especially for corticosteroid-insensitive neutrophilic airway inflammation.

Removal of Cr (VI) from aqueous solution using magnetic biochar synthesized by a single step method

Abstract: Magnetic biochar, as an adsorbent, was synthesized by a single step method, where iron salt was directly mixed with pinewood sawdust by chemical co-precipitation and subsequently pyrolyzed at 700°C for Cr (VI) removal from aqueous solution. The effects of some important parameters including adsorbent dosage (0.4–2.8 g/L), pH (1–10) of the solution, contact time (0–1440 minutes), initial concentration (30–120 mg/L), and temperature (20–40°C) were investigated in batch experiments. Both pre- and post-adsorbents were characterized by SEM-EDX and XPS to investigate the adsorption mechanism. The maximum adsorption capacity of the tested magnetic biochar under the certain experimental conditions determined as optimal was 42.7 mg/g for Cr (VI). The adsorption data were proved to be suitable for the pseudo-second order model for kinetics and the Langmuir model for isotherms with correlation R2 = 0.9996 andR2 > 0.9980, respectively, after fitting with four kinetic models (pseudo-first order, pseudo-second ...

Main characteristics of suction control of flow separation of an airfoil at low Reynolds numbers

Abstract: The suction control of flow separation of a NACA0012 airfoil is studied numerically for Reynolds number Re=104, angle of attack α = 2 ° , 4°, 6°, and 8°, and Re=105, α = 4 ° . The suppression effects of suction are studied considering many parameters such as suction coefficient, location, angle, hole width, and porosity. The variations in energy consumption and lift–drag ratio during the control process are used for evaluating the control effects.

Proteomic analysis of sputum reveals novel biomarkers for various presentations of asthma.

Abstract: It is now recognized that asthma can present in different forms. Typically, asthma present with symptoms of wheeze, breathlessness and cough. Atypical forms of asthma such as cough variant asthma (CVA) or chest tightness variant asthma (CTVA) do not wheeze. We hypothesize that these different forms of asthma may have distinctive cellular and molecular features. 30 patients with typical or classical asthma (CA), 27 patients with CVA, 30 patients with CTVA, and 30 healthy control adults were enrolled in this prospective study. We measured serum IgE, lung function, sputum eosinophils, nitric oxide in exhaled breath (FeNO). We performed proteomic analysis of induced-sputum supernatants by mass spectrometry. There were no significant differences in atopy and FEV1 among patients with CA, CVA, and CTVA. Serum IgE, sputum eosinophil percentages, FeNO, anxiety and depression scores were significantly increased in the three presentations of asthmatic patients as compared with healthy controls but there was no difference between the asthmatic groups. Comprehensive mass spectrometric analysis revealed more than a thousand proteins in the sputum from patients with CA, CVA, and CTVA, among which 23 secreted proteins were higher in patients than that in controls. Patients with CA, CVA, or CTVA share common clinical characteristics of eosinophilic airway inflammation. And more importantly, their sputum samples were composed with common factors with minor distinctions. These findings support the concept that these three different presentations of asthma have similar pathogenetic mechanism in terms of an enhanced Th2 associated with eosinophilia. In addition, this study identified a pool of novel biomarkers for diagnosis of asthma and to label its subtypes. Trial registration http://www.chictr.org.cn (ChiCTR-OOC-15006221)

Discrete Boltzmann method with Maxwell-type boundary condition for slip flow

Abstract: The rarefied effect of gas flow in microchannel is significant and cannot be well described by traditional hydrodynamic models. It has been know that discrete Boltzmann model (DBM) has the potential to investigate flows in a relatively wider range of Knudsen number because of its intrinsic kinetic nature inherited from Boltzmann equation. It is crucial to have a proper kinetic boundary condition for DBM to capture the velocity slip and the flow characteristics in the Knudsen layer. In this paper, we present a DBM combined with Maxwell-type boundary condition model for slip flow. The tangential momentum accommodation coefficient is introduced to implement a gas-surface interaction model. Both the velocity slip and the Knudsen layer under various Knudsen numbers and accommodation coefficients can be well described. Two kinds of slip flows, including Couette flow and Poiseuille flow, are simulated to verify the model. To dynamically compare results from different models, the relation between the definition of Knudsen number in hard sphere model and that in BGK model is clarified.

CDK1 promotes nascent DNA synthesis and induces resistance of cancer cells to DNA-damaging therapeutic agents

Abstract: Cyclin dependent kinase 1 (CDK1) is essential for cell viability and plays a vital role in many biological events including cell cycle control, DNA damage repair, and checkpoint activation. Here, we identify an unanticipated role for CDK1 in promoting nascent DNA synthesis during S-phase. We report that a short duration of CDK1 inhibition, which does not perturb cell cycle progression, triggers a replication-associated DNA damage response (DDR). This DDR is associated with a disruption of replication fork progression and leads to genome instability. Moreover, we show that compromised CDK1 activity dramatically increases the efficacy of chemotherapeutic agents that kill cancer cells through perturbing DNA replication, including Olaparib, an FDA approved PARP inhibitor. Our study has revealed an important role for CDK1 in the DNA replication program, and suggests that the therapeutic targeting CDK1 may be a novel approach for combination chemotherapy.

Discrete ellipsoidal statistical BGK model and Burnett equations

Abstract: To simulate non-equilibrium compressible flows, a new discrete Boltzmann model, discrete Ellipsoidal Statistical(ES)-BGK model, is proposed. Compared with the original discrete BGK model, the discrete ES-BGK has a flexible Prandtl number. For the discrete ES-BGK model in Burnett level, two kinds of discrete velocity model are introduced; the relations between non-equilibrium quantities and the viscous stress and heat flux in Burnett level are established. The model is verified via four benchmark tests. In addition, a new idea is introduced to recover the actual distribution function through the macroscopic quantities and their space derivatives. The recovery scheme works not only for discrete Boltzmann simulation but also for hydrodynamic ones, for example, based on the Navier-Stokes, the Burnett equations, etc.

The efficacy and safety of tivantinib in the treatment of solid tumors: a systematic review and meta-analysis.

Abstract: Background Tivantinib was designed to kill cancers by targeting the mesenchymal-epithelial transition (MET) protein. Although numerous tivantinib clinical trials are ongoing, tivantinib's efficacy and safety are still not clear. This meta-analysis was done to evaluate tivantinib's efficacy and safety in solid tumor treatment. Materials and methods PUBMED, EMBASE, and other databases were searched for eligible tivantinib clinical trials. The hazard ratio (HR) and 95% confidence interval (CI) of progression-free and overall survival (PFS and OS, respectively) were pooled and analyzed to evaluate tivantinib's efficacy. Data concerning adverse events (Grade ≥ 3) were pooled to calculate relative risks (RRs) with 95% CI for tivantinib-treated compared with control arms. Findings Patients (1824) from six randomized control trials (RCTs) were enrolled. Compared with controls, tivantinib produced a significant improvement in PFS (HR, 0.73; 95% CI 0.65-0.83) but not in OS. In the non-small-cell lung cancer (NSCLC) subgroup, tivantinib combined with erlotinib prolonged patients' PFS when compared with controls (HR, 0.75; 95% CI, 0.65-0.86). In the white population, tivantinib also significantly improve PFS between treatment and control arms (HR, 0.75; 95% CI, 0.65-0.87). Tivantinib significantly improved OS in patients with high levels of MET expression. Tivantinib was shown to increase the risk of anemia and neutropenia. Interpretation Tivantinib was better in prolonging PFS (not OS) in patients with solid tumors. High MET expression cancers may benefit from tivantinib. Tivantinib appeared to be well-tolerated by patients.

Deletion of Shp2 in bronchial epithelial cells impairs IL-25 production in vitro, but has minor influence on asthmatic inflammation in vivo.

Abstract: Shp2 played an important role in cigarette-smoke-mediated inflammation, surfactant homeostasis and asthmatic airway remodeling. However, whether shp2 plays a key role in epithelium-associated allergic reaction is still unknown. In this study, LPS and OVA were observed to induce the production of IL-25 in bronchial epithelial cells in vitro via the activation of MAPK p38 and JNK. Furthermore, blockage of Shp2 by its specific inhibitor PHPS1 or by siRNA-mediated depletion was found to reduce the production of IL-25 in epithelial cells as well as the up-regulated LPS-triggered activation of JNK but not p38. To confirm the role of intra-bronchial epithelial Shp2 in OVA-induced allergic reaction, we generated CC10-rtTA/(tetO)7-Cre/Shp2f/f mice, where Shp2 was conditionally knocked out in bronchial epithelial cells. Surprisingly, specific deletion of Shp2 in bronchial epithelial cells showed a mild but insignificant effect on the expressions of epithelium-derived cytokines as well as TH2 and TH17 polarization following allergen-induced murine airway inflammation. Collectively, our data suggested that deletion of Shp2 impaired IL-25 production in bronchial epithelial cells in vitro, but might yet have minor influence on OVA-induced allergic reaction in vivo.

Do Firms Obtain Multiple Ratings to Hedge against Downgrade Risk

Abstract: Utilizing a quasi-natural experiment, the 2005 Lehman index rule change, we study the role of multiple rating in corporate hedging. We find U.S. firms exhibit a sharp increase in their demand for a third rating after the event, with this pattern especially significant for firms near a rating downgrade. Open-ended mutual funds also increase their holdings of three-rating bonds. Institutional investors in general trade three-rating bonds more actively. These findings suggest that firms use multiple ratings to maintain a stable rating status, which helps both firms and institutional investors avoid the costly consequences of a rating downgrade.

Activating Transcription Factor 3 Is Essential for Cigarette Smoke-Induced Mucin Expression via Interaction with Activator Protein-1.

Abstract: Mucus hypersecretion is an important pathologic feature of chronic obstructive pulmonary disease. Activating transcription factor 3 (ATF3) is an adaptive-response gene that participates in various cellular processes. However, little is known about its role in cigarette smoke (CS)-induced mucus hyperproduction. This study aimed to investigate the role and molecular mechanisms of ATF3 in CS-induced Mucin 5AC (MUC5AC) expression. ATF3 was elevated in lung tissues of mice exposed to CS for 12 weeks. Treatment with CS extract significantly induced ATF3 expression and MUC5AC production in human bronchial epithelial cells, NCI-H292, and mouse tracheal epithelial cells. Interference of ATF3 significantly attenuated CS-induced MUC5AC expression in NCI-H292 and human bronchial epithelial cells. Mouse tracheal epithelial cells isolated from Atf3−/− mice also exhibited less MUC5AC production in response to CS extract treatment. In vivo, the Atf3−/− mice also displayed a significantly reduced mucus production relative to wild-type controls in response to chronic CS exposure. Furthermore, a chromatin immunoprecipitation assay revealed increased ATF3 binding to the MUC5AC promoter after CS treatment, and this transcriptional binding was significantly inhibited by knockdown of JUN, a subunit of activator protein-1. These results demonstrate that ATF3 may be involved in activator protein-1 signaling and transcriptional promotion of CS-induced MUC5AC expression in airway epithelial cells.

The influence of magnetic field on the physical explosion of a heavy gas cloud

Abstract: Richtmyer–Meshkov RM instability arises during the eruption of heavy gas cloud. In this study, we numerically study the effects of magnetic fields on the RM instability induced by the ionised cylindrical and spherical heavy gas cloud eruption using corner transport upwind + constrained transport algorithm. Our numerical results show that magnetic fields can suppress the formation of spike and bubble structures induced by the eruption in both cylindrical and spherical cases . The magnetic pressure of the interface along the perpendicular direction of magnetic field is the main factor to control the distortion of the interface. Even weak magnetic fields can drastically alter the evolution of the cloud and result in different distributions and amplifications of the magnetic pressure, which will affect further transformation of RM instability during the ionised gas eruption. Meanwhile, the magnetic pressure on the interface decreases gradually when the initial magnetic field is relatively large; when the initial magnetic field is small enough, the opposite results will occur.

Driving factors of interactions between the exchange rate market and the commodity market: A wavelet-based complex network perspective

Abstract: In traditional econometrics, a time series must be in a stationary sequence. However, it usually shows time-varying fluctuations, and it remains a challenge to execute a multiscale analysis of the data and discover the topological characteristics of conduction in different scales. Wavelet analysis and complex networks in physical statistics have special advantages in solving these problems. We select the exchange rate variable from the Chinese market and the commodity price index variable from the world market as the time series of our study. We explore the driving factors behind the behavior of the two markets and their topological characteristics in three steps. First, we use the Kalman filter to find the optimal estimation of the relationship between the two markets. Second, wavelet analysis is used to extract the scales of the relationship that are driven by different frequency wavelets. Meanwhile, we search for the actual economic variables corresponding to different frequency wavelets. Finally, a complex network is used to search for the transfer characteristics of the combination of states driven by different frequency wavelets. The results show that statistical physics have a unique advantage over traditional econometrics. The Chinese market has time-varying impacts on the world market: it has greater influence when the world economy is stable and less influence in times of turmoil. The process of forming the state combination is random. Transitions between state combinations have a clustering feature. Based on these characteristics, we can effectively reduce the information burden on investors and correctly respond to the government’s policy mix.

Flow separation control of two kinds of microvortex generators for a supersonic spinning projectile

Abstract: Previous studies have shown that Microvortex generators (MVGs) can effectively control the flow separation of supersonic boundary layer. To improve the flight stability of a spinning projectile, two kinds of MVGs, micro ramps and vanes, are applied to control the flow separation of an original standard 155 mm projectile, respectively. Numerical simulations were performed with the use of Detached eddy simulation (DES) method, and the flow fields of the projectile with and without micro MVGs were simulated, the characteristics of the boundary layer and aerodynamic data of three cases were compared and discussed. The numerical results reveal that the effect of the MVGs control is obvious, but their mechanisms are different, and the vanes are more effective than the ramp in the boundary layer control. However, they can both improve the lift and pitching moment of the projectile, and eliminate their oscillations; as a result, its flight stability and firing dispersion can be enhanced. Our results can provide important guidance for improving the flight quality of supersonic projectiles.

Investigations of Shock Wave Reflection and Focusing in Different Triangle Wedges

Abstract: Based on the large eddy simulation, combined with the fifth-order WENO scheme and the AMR technology, the phenomena of shock wave reflection and focusing in the triangular wedges with various semi-apex angle have been numerically simulated under the condition that Mach number is 6. The numerical results reveal that the change of the half-corner angle has an apparent influence on the kind of shock reflection. The type of reflection transforms from Mach reflection to double-Mach reflection when the semi-apex angle increases from 300 to 500 and the pressure behind the slipstream becomes higher resulting in making the wall-jetting clear.

Do Firms Obtain Multiple Ratings to Hedge against Potential Downgrade

Abstract: Utilizing a quasi-natural experiment, the 2005 Lehman index rule change, we study the role of multiple rating in corporate hedging. We find U.S. firms exhibit a sharp increase in their demand for a third rating after the event, with this pattern especially significant for firms near a rating downgrade. Open-ended mutual funds also increase their holdings of three-rating bonds. Institutional investors in general trade three-rating bonds more actively. These findings suggest that firms use multiple ratings to maintain a stable rating status, which helps both firms and institutional investors avoid the costly consequences of a rating downgrade.